Discovered some ‘play’ in the crank arms while riding and realised that the drive side BB shell had worked itself loose while riding. 🙁

On returning home I’ve tried re-fitting the drive side BB shell, but it just ‘slides’ in and out, only slightly holding, maybe for the last few threads.

I tried re-fitting another new BB shell and this is much better – yay 😀 ! I can get it up good and tight, no worries, but compared with the non-drive side there is a slightly noticeable ‘wobble’ on tightening, however, this disappears once the shell is done up tight.

I’ve read about getting BB thread ‘chased’ at my LBS – will this help? Or is this just for cleaning grotty threads?

Surely it can’t be possible to ‘magic’ thread material (from nothing) by this means?

Any other ideas?

Lots of loctite?

Get a decent lbs to helicoil it.

It has to be worth getting your shop to run a chase through it, although the fact that the cup slides in doesn’t bode well.

Somewhere like Betd will probably be able to save the frame with a threaded insert – for around £100, if I remember correctly. What make of BB is it? Some cups use longer threaded portions (Saint and RaceFace, perhaps). I can still see them working loose over time, but it’s got to be worth a try.

Go square taper with this £15 option?

Arrrghh.. no, square taper is not an option! 🙂

I’m saving the whole ‘threaded insert’ option as a last resort. It’s a pain in the ass to have to send the frame away TBH and I’ve only just got it back from a re-spray 🙄

Given that a new BB shell with undamaged threads seems to go on tight ok, I’m hoping I’ll be able to use a shed-load of loctite and that’ll hold it for a bit, and maybe having the threads re-tapped / ‘chased’ beforehand might give it a fighting chance also?

You could also try a deeper BB, IIRC Saint has a deeper driveside thread.

PS don’t use a shedload of loctite, a little might be a good idea but a lot will just make it a bollocks to get the BB back out, which might end up damaging the thread even worse. Personally I’d get it chased, by a mechanic you really trust, though it might not actually make any difference.

Those yst brackets are not very good and come undone even if loctite is used

Personally I wouldn’t go down the loctite solution, get a decent LBS to retap it (£10 approx.). Gut feeling is that what you describe is beyond a retap, so helicoil might be the solution, investigate a retap first tho.
It’s only an idea, but beyond that, maybe investigate an alteration to press fit BB, I don’t know if this is possible.
I’m in a similar situation, bought a 2nd hand frame and one of the BB threads had obviously been cross threaded by some ham fisted idiot. Luckily, it was just very tight to screw in by hand, I think it will be re-tapable when the bb needs replacing.

Try a Saint bb or a Raceface fr/dh deep fit BB